The scientists trained 13 dogs to lie motionless inside an fMRI machine, in order to probe how they process human speech.
Photograph: Vilja and Vanda Molnár

It is both what you say and the way that you say it that matters when it comes to communicating with man’s best friend, research has revealed.

Scientists from Hungary scanned the brains of dogs while each was played the sound of their trainer’s voice, and discovered that our canine companions only experience a sense of reward when both the words and intonation indicate praise.

The team also found that dogs process speech in a similar way to humans, processing meaningful words with their left hemisphere and intonation with a region in their right hemisphere.

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“The results were very exciting and very surprising,” said lead researcher Attila Andics from Eötvös Loránd University in Budapest.

Writing in the journal Science, Andics and colleagues describe how they trained 13 dogs over a period of months to lie motionless inside an fMRI machine, in order to probe how they process human speech.

The researchers used the scans to look at how their brain activity changed as they were played recordings of their trainers’ voices through a pair of headphones. Four different recordings were played with either praise words (such as “well done!”) or neutral words (such as “however” or “nevertheless”) coupled with either a high-pitched intonation indicative of praise, or a neutral intonation.

The results revealed that compared to neutral words, praise words resulted in an increase in activity in the left hemisphere of the brain for both types of intonation, suggesting that, like humans, dogs use the left side of their brain to process words that they have recognised and attach meaning to. On the other hand, differences in intonation but not word type, resulted in a change in activity in an area within the auditory region of the right hemisphere.

“It is actually the very same part of the brain in this right auditory brain region that we found in dogs and also humans in an earlier study that responds to the emotional content of a sound,” said Andics. “It is not a mechanism that is only there for language stimuli, it is the same mechanism dogs use for processing emotional sounds in general.”

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The researchers also looked at the reward centre in the doggy brain, an area that responds to activities or experiences deemed pleasurable.

The results reveal that the reward centre only shows an increase in activity when both praise words and praise intonation are used.

“From this research, we can quite confidently say if they only hear you then it is not only how you say things but also what you say that matters to them,” said Andics.

But, says Andics, whether a dog can really tell if you are calling it a smelly hound in a jolly voice is another matter, as there are typically other cues, such as body language and facial expression at play.

The research, says Andics, offers new insights into the evolution of language.

“The neural mechanism humans have for processing meaning in speech, so for processing word meaning and intonation, are not uniquely human - they seem to be there in other species,” said Andics. That, he adds, suggests that our use of words was down to a novel idea, rather than new brain mechanisms. “It is not the result of a special new neural mechanism but the result of an innovation,” said Andics. “We invented words as we invented the wheel.”